Propulsion nozzles

ABSTRACT

The disclosure shows a propulsion nozzle having angularly spaced afterbodies projecting downstream of the convergent portion of the nozzle. Secondary flaps are pivotally mounted between the afterbodies, forming, in combination therewith, a divergent nozzle portion for maximum supersonic exhaust gas velocities. The flaps are pivoted inwardly to aerodynamically reduce the nozzle exit area for reduced exhaust gas velocities, particularly for subsonic flight. The flaps may be pivoted further inwardly against a central plug to block rearward gas flow and produce reverse thrust. The pivotal mountings of the flaps form a structural hoop, and the actuators for the flaps are mounted within the afterbodies. Alternate forms of flaps and hoop means are shown as well as features of cooling air conservation.

United States w t unasessw [72] Inventors Werner E. llowald; 3,346,193 10/1967 Tumicki 239/265.41 X Elmore Verne Sprunger, both of 3,432, l 00 3/1969 Hardy et al. 239/2 Cincifinafi- FOREIGN PATENTS {5;} 25$ 332 17 895,331 5/1962 Great Britain 239/265.l7 5] Patented A g- 1 1 1 Primary ExaminerM. Henson \vVoodJrv [73] Assignee General Electric Co. Assistant Examiner-Edwin D. Grant AttorneysDerek P. Lawrence, E. S. Lee, lll, Lee H. Sachs,

Frank L. Neuhauser, Oscar B. Waddell and Joseph B. [54] PROPULSION NOZZLES Folman 24 Claims, 19 Drawing Figs. [52] US. Cl ..239/265.l9, BSTRACT; Th di lo how a propulsion nozzle having 239/265-33, 60/229 angularly spaced afterbodies projecting downstream of the [5 l 1 hf. Cl Convergent rtio of the ale Secondary flaps are {50] Field at Search ..239/265.l9, pivomny mounted between the anal-bodies, forming, i 26515'265-27265'29-265-3112653316537 bination therewith, a divergent noule portion for maximum 265-391265-4l;60/228- 229, 230; Isl/33222; supersonic exhaust gas velocities. The flaps are pivoted in- 244/1103 wardly to aerodynamically reduce the nozzle exit area for reduced exhaust gas velocities, particularly for subsonic flight. [561 References The flaps may be pivoted further inwardly against a central UNITED STATES PATENTS plug to block rearward gas flow and produce reverse thrust. 3 2/19 1 C Y S 6t 239/265.39 The pivotal mountings of the flaps form a structural hoop, and 2.346.164 9 8 a r 239/265.39 the actuators for the flaps are mounted within the afterbodies. 3 19 0 alf d e alm- 239/26539 Alternate forms of flaps and hoop means are shown as well as 3,279,! 82 10/1966 Helmintoller 239/265.l9 X features of cooling air conservation- PATENTED-AUG 1 019?:

SHEET 1 [IF 6 INVENTORj. WERNEE E. HOWALD ELMOEE VEENE PEUQGER BY 42- PATENIEDMIBIOM 3,598,319

SHEET 2 OF 6 INVENTORS. WERNER E. HOWALD ELMOEE V52 5920 GE R PATENTED AUG 1 0 l9?! SHEET 0F 6 11 I l I I I I I '1 IIIIIIIIIIIIIIIIIIIIIIII 1' lrlllllm WERNER E. HOWRLD lE3M0RE VE NE SPRUNGEE PATENIEU Anal 0 ran sum 5 0F 6 INVENTORJ. ER E. HOWALD ELMORE VERNE SPEUNGER 4 770IA/ty PATENTEU mm 01911 SHEET 8 OF 6 INVENTORS WERNER E. HOWALD EL MORE VEBNE SPRUNGER PROPULSION NOZZLES The present invention relates to improvements in propulsion nozzles used in fluid reaction engines, as exemplified by turbojet engines.

It is fundamental that a gas stream must be accelerated through a convergent nozzle and then expanded through a divergent nozzle to obtain the supersonic hot gas stream velocities requisite for supersonic flight speeds. To efficiently obtain higher gas stream velocities for high Mach. No. flight, the ratio of the discharge area of the divergent nozzle portion to the discharge area of the convergent nozzle portion must be increased. Recognizing that the hot gas stream will separate from and lose its efficiency if the angle of divergent nozzle portion exceeds a given length, it will be apparent that propulsion nozzles for high Mach. No. flight become quite long and increase the weight of the overall propulsion system.

Supersonic nozzles pose a serious problem in obtaining efficient operation at subsonic flight conditions, since efficient operation in that regime requires discharge of the hot gas stream from a convergent nozzle.

The conventional approach to providing propulsion nozzles with both subsonic and supersonic capabilities has been to form the divergent nozzle portion with a plurality of flaps which are collapsed inwardly to an area approximating that of the convergent nozzle portion during subsonic flight. Such an approach has been found aerodynamically effective but energy requirements for translating the flaps, as well as weight, are significantly increased, particularly as the area ratio of the nozzle is increased.

A further shortcoming of prior nozzles with both subsonic and supersonic capabilities has been their lack of thrust reversal capability, at least insofar as operational, high-performance aircraft are concerned, in spite of the many proposals found in the patent art, as well as elsewhere. This is attributable to the fact that for such prior proposals, reverse thrust capability involved excessive weight or performance penalties for operational acceptance. The alternative has been to employ drag parachutes and other arresting devices when an aircraft is landing.

One object of the invention is to improve the efficiency of propulsion nozzles having operational capabilities at both subsonic and supersonic flight conditions and, in so doing, reduce the length and weight of such nozzles.

Another object of the invention is to attain the above ends and, additionally, provide reverse thrust capability with little or no weight or performance penalties.

Additionally, it is an object of the invention to attain the above ends in a manner consistent with aircraft engine system requirements, as exemplified by low noise, high reliability, long life and installation compatibility.

These ends are attained by a propulsion nozzle comprising a convergent nozzle portion and a plurality of flaps projecting downstream therefrom. Afterbodies, disposed downstream of the flaps are angularly spaced about the longitudinal axis of the convergent nozzle portion and have inner surfaces divergent therefrom. Flaps are respectively mounted between these afterbodies to form, in combination with afterbodies, an uninterrupted, divergent nozzle of maximum exit area. The flaps are displaceable to positions wherein their upstream ends capture air and introduce it along the inner surfaces of the flaps. As this occurs, the downstream ends of the flaps move inwardly so that the effective exit area is reduced both aerodynamically and mechanically.

Preferably a central plug is employed to reduce nozzle length by the provision of a second expansion surface. The provision of a plug also permits the inner ends of the flaps, preferably having lateral wings, to be swung further inwardly so that the rearward flow of the hot gas stream is blocked and the gas stream discharged laterally and forwardly to provide reverse thrust.

Where the engine is pod mounted on an aircraft wing, the outer surfaces of the afterbodies form continuations of the pod. The afterbodies also extend upstream of the convergent nozzle portion. Ramps, between the afterbodies, slope inwardly from their upstream ends to facilitate the introduction of air along the inner surfaces of the flaps when they are displaced to subsonic operating positions.

Actuators for positioning the flaps are mounted within the afterbodies, eliminating drag or special housings normally associated with nozzle actuation systems. Preferably the flaps are pivotally mounted on the afterbodies and v the pivotal mountings, in combination with the afterbodies, provide a structural hoop for the cantilevered afterbodies.

The invention also includes other important features which will be apparent from a reading of the following description of the disclosure found in the accompanying drawings. The novelty of all features is pointed out in the appended claims.

In the drawings:

FIG. 1 is a simplified outline illustration of an engine mounted on the wing of an aircraft with a propulsion-nozzle, embodying the present invention;

FIG. 2 is a simplified perspective view, with portions broken away, of the exhaust nozzle seen in FIG. I;

FIG. 3 is an elevation, partially in section, illustrating the supersonic mode of operation of this nozzle;

FIG. 4 is a partial end view of the nozzle as seen in FIG. 3;

FIG. 5 is an elevation, partially in section, illustrating the subsonic mode of operation of the nozzle;

FIG. 6 is a partial and view of the nozzle in its subsonic mode of operation;

FIG. 7 is an elevation, partially in section, illustrating the reverse thrust mode of operation of the nozzle;

FIG. 8 is a partialend view of the nozzle in its reverse thrust mode;

FIG. 9 is a simplified half section of an alternative nozzle construction;

FIG. 10 is a simplified, half section of another alternative nozzle construction;

FIG. 11 is a more detailed, longitudinal section, through a portion of the nozzle;

FIG. 12 is a further enlarged, longitudinal section, illustrating in greater detail an actuator seen in FIG. 11;

FIG. 13 is a section, taken on line XIII-XIII in FIG. 12;

FIG. 14 is a section on an enlarged scale, taken on line XIV-XIV in FIG. 11;

FIG. 15 is a section taken on line XV-X V in FIG. 14;

FIG. I6 is a section similar to FIG. 15, illustrating an alternate actuator position;

FIG. 17 is a section, taken on line XVII-XVII in FIG. 14;

FIG. 18 is a view, taken on line XVIII-XVIII in FIG. 17; and

FIG. 19 is a perspective view, with portions broken away, of another alternate nozzle construction.

FIG. I diagrammatically illustrates the installation of a podmounted gas turbine engine employing a propulsion nozzle embodying the present invention. An aircraft wing I0 is shown, in section, with a pylon I2 providing the structural connection to a generally cylindrical pod I4. A typical supersonic inlet 16 is formed at the forward end of the pod by an inlet spike I8. Air flows from the inlet I6 to a gas turbine engine 20, which is illustrated as conventionally comprising a compressor 22 for pressurizing air, a combustor 24 wherein the pressurized air supports combustion of fuel to generate a hot gas stream, and a turbine 26 which is driven by the hot gas stream to power the compressor. The remaining energy of the hot gas stream is converted to a propulsive force by a nozzle 28 which will be described in greater detail.

Before leaving FIG. 1, it will be noted that the casing of engine 20 is spaced from the inner surface of the pod 14 to pro vide a flow path for what is herein referenced as secondary air." Thus, a small portion of the air entering the inlet I6 bypasses the engine 20 and enters the nozzle 28 in a manner and for purposes later described.

The nozzle 28 is of the convergent-divergent type employing a central plug 30. As is better illustrated in FIG, 2, the nozzle 28 comprises a plurality of fixed, angularly spaced afterbodies 32. A flap 34 is pivotally mounted, at 35, between each adjacent pair of afterbodies, leading to flaps 38 which form the convergent portion of the nozzle 28. I

The outer surfaces of the afterbodies 32 are formed as aerodynamic continuations of the nacelle, maintaining substantially the same diameter. The inner surfaces of the afterbodies form fixed, divergent nozzle surfaces 40. The afterbodics 32 overlie the convergent nozzle flaps 38 as theyextend upstream. for attachment to the engine casing. I

In the supersonic mode of operation, as illustrated in FIG. 2, the inner surfaces of the flaps 34 are aligned with the divergent nozzle surfaces 40 of the afterbodies 32, thus providing,

in combination with the convergent flaps 38, an ideal nozzle surface for supersonic flight. It will be seen that there aresmall dips in the outer surface of the nozzle, due to the thin airfoil shape of the flaps 34. These dips have been found to have little or no effect on installed performance of the nozzle.

FIGS. 3 and 4 further illustrate the supersonic mode of operation of this nozzle. The hot gas stream, dischargedfrom the engine or gas generator, enters the convergent portionof the nozzle, formedby the flaps 38 and plug 30, andis then expanded against the plug and the divergent portion of thenozzle, formed by the flaps 34 and afterbodies 32. It will also be seen that secondary air is ejected over the outer surfaces of the flaps 38.

FIGS. 5 and 6 illustrate the subsonic mode of nozzle opera-;;.

tion wherein the flaps 38 have been pivoted to adjust the convergent discharge exit area for reduced flight velocity,.consistent with the cycle requirements of the engine. The flaps 34 are pivoted to the approximate positions shown in FIG. 5. When so positioned, large amounts of ambient or tertiary air are captured by the outer ends of the flaps and directed'along their inner surfaces. This tertiary air forms an aerodynamic surface which controls flow of the hot gas stream and prevents its overcxpansion or, at least. minimizes such ovcrcxpansion and consequent loss of propulsion efficiency. The aerodynamic effect of the tertiary air is enhanced by the flow of secondary air between the convergent nozzle flaps 38 and the ramps 36. This secondary air flow also prevents the outer surfaces of the flaps 38 from inducing an undesirable drag effect.

The nozzle 28, as thus described, is highly efficient in both supersonic and subsonic flight regimes. The preferred use of a plug in the nozzle minimizes overall nozzle length, and this minimizes the length of the flaps 34 for a given expansion ratio. Not only do the flaps have a low weight and small angle of movement, but further there are a minimum number of flaps that are translated in transitioning between supersonic and subsonic operation. All of this minimizes the complexity and power requirements of the actuator system, later described, for controlling movement of the flaps 34.

Another factor to be noted in connection with the flaps 34 is that their thin airfoil shapes minimize losses in the tertiary airflow, thereby optimizing the nozzle for subsonic operation.

A further advantage of the described nozzle is its reverse thrust capabilities. That is, simply pivoting the flaps 34 beyond their subsonic positions provides blockage for the hot gas stream. The gas stream is thus deflected laterally and forwardly along the undersides of the flaps 34 for discharge between the afterbodies 32, as seen in FIG. 7. The spacing between the end of each rump 36 and the pivot point for the associated flap 34 automatically provides discharge openings for hot gas flow while the angle of the flaps 34 properly directs the hot gas flow to produce reverse thrust. The need for thrust reverser cascades is thus eliminatedin most, if not all, cases.

It will be noted that the flaps 34 preferably have wedgeshaped wings 42. These wings provide substantially complete blockage of the hot gas stream in the reverse thrust mode, as

will be seen from FIG. 8. In the subsonic mode the wings 42 assist in diverting tertiary air in aerodynamically reducing the nozzle discharge opening. In the supersonic mode, these flaps flaps 34' would be predicated on optimization of the nozzle for supersonic flight.

FIG. I0 illustrates another alternate nozzle construction wherein the convergent nozzle flaps 38 form the downstream portions of ramps 36'. This construction would be used where secondary airflow requirements over the outer surfaces of these flaps were eliminated or minimal. Otherwise, this nozzle has the same functional capabilities as described in connection with the embodiments of FIGS. l9.

The preceding aerodynamic aspects of the inventiona're ad- 'vantageously implemented by constructional features relating to the actuation of the flaps 34 and 38 as well as the fabrication of the afterbodies 32, as will be apparent from the following description. Thenozzle 28 may comprise a ringlike casting 46 (FIG. 11) bolted to and forming a part of the engine frame structure.

I The ramps 36, in this event, are formed integrallywiththering and the upstream ends of the afterbodies 32(see also FlG. I3)."Thje remaining, cantilevered portions of the afte'rbodies "may then be bolted or otherwise secured to this ring structure,

"as castings 4'7.

" The radial height of the afterbodies is sufficient to accommodate actuators 48 and 50 which are respectively employed to position the flaps 38 and 34. By so mountingthese actua tors, they are removed from any fluid flow stream, and thus a potential source of energy loss is eliminated. T

Theflaps 38 are slightly narrower than the afterbodies and the spaces thercbctwcen. A flap 38 is pivotally mounted on the frame 46 beneath each afte'hod and each intervening space. Half-round bars 51 (FIG. I2) are used forthis purpose to retain the rounded ends of these flaps in curved seats 52, secured to the frame 46. The flaps are interconnected by seals, comprising female sealing members 54 (FIG. 13), secured to the flaps between the spaces, and male sealing members 56, secured to the flaps beneath the aftcrbodies.

The cylinder of each actuator 48 is mounted by trunnions 58 on a spherical shell 60, which, in turn, is mounted on a tube 61, opening onto the inner surface of the afterbody 32. The piston rod 62 of each actuator receives a pin 64 secured to the adjacent flap 38. Thus, alternate flaps 38, beneath the afterbodies 32, are connected to the respective actuators 48, within the afterbodies. When the piston rods are extended, all of the flaps will simultaneously pivot inwardly, taking note of the fact that the interdigitating seal members 54 and 56 carry the unpowered flaps 38 with the flaps 38 which are connected to the actuators 48. Similarly, when the piston rods 62 are retracted, all of the flaps 38 pivot outwardly to the full line positions shown in FIGS. 12 and 13.

The hydraulic system for controlling movement of the actuators may be of conventional design to regulate flow of hydraulic fluid to position the flaps 38 in accordance with the desired operating conditions of the engine.

The secondary flaps 34 are pivotally mounted between the aftcrbodics 32 in the fashion now to be described with reference to FIGS. 14-18. Each flap 34 comprises an appropriately ribbed, frame structure including an integral cross shaft 66. A face spline 68 is formed at the opposite ends of the shaft 66. A hollow bellcrank 70 has a corresponding face spline engaging the face spline 68. Differentially threaded screws 72 hold these face splines in engagement and securely attach the bellcranks 70 to the opposite ends of the shaft 66. The bellcranks 70 are journaled in afterbody bushings 74 having flanges 76 which the bellcranks 70 engage to take force loads in an axial direction.

"wrench to ohtain'apredetermined preload on-theteeth of the The bellcranks 70 are connec ed by pins 78 to .the.;piston rods 80 of the actuators 50. Each actuator cylinder has integral trunnions 82 which are pivotally received at the junc ture between the frame casting 46 and the afterbody castings 47. it will be seen that pressurization of the-actuators 50 to ex tend the piston rods 80 causes the downstream ends of the flaps 34 to pivot inwardly. I y l a 1 While the broader aspects of the invention are not necessarily so limited. it is preferred that the flaps 34 pivot simultaneously for axisymmetric thrust characteristics of the no'zzle. To this end, a bevel gear segment 84 is secured to the end face of each bellcrank 70 and meshes with thegearsegment secured to the adjacent bellcrank. This geared connection between the flaps plus commonpressurizationpressures for the several actuators 50 assure the I desired simultaneous movement of the flaps 34. The hydraulic system'for the several actuators may be of conventional design to regulate fluid so as to properly position the flaps 3'4 for a desired engine operating condition.

The described actuation system has severaladv'antages in employing actuator inputs to oppositeends of the shaft 66,

The force loadings are thereby balanced to eliminate any tendency of the flaps to twist. The diameters of the'actuators as well as the required hydraulicpressure levels are minimized by splitting the required force between two actuators. Finally, the

redundancy of the several actuators and the gear interconnection between the flaps provide greater system reliability in the event of failure of a single actuator. i

Another feature of the described flap mounts is thatthey tie the afterbodies together with a structural hoop. During engine operation there are substantial gas pressure loadings which act on the flaps and aftcrbodics with radially outward components. These forces are taken in part between the bellcranks 70 and the bushing flanges 76, through the afterbody structure and through the flap shafts 66, which compositcly form a structural hoop. This arrangement, among other advantages, minimizes the cantilevered force loadings that would otherwise have who carried from the aftcrbodies into the ringlike frame structure 46 and the consequent increased weight of both the frame and the afterbodies. This structural hoop also minimizes any tendency of the downstream ends of the flaps 34 and afterbodies 32 to spread apart and the resultant thrust losses in a supersonic flight regime. As can be seen from FIG. 14, such losses are also minimized by the provision of honeycomb seals 86 on the side faces of the flaps 34.

The described connection of the bellcr'anks 70 to the flaps 34 further permits removal and/or replacement of individual flaps for anymaintenance that might be required. This will be apparent from the following description of 'th one of the bcllcranks 70 to its flap 34.

lnitiallythe flap 34 is positioned between the afterbodies 32 with a cover plate 88 removed from the outer surface of the afterbody. The hollow screw 72 is threaded fully into the bellcrank sothat the internal threads of the bellcrank register with the groove 90 between the two sets of threads on'the'screw 72. v; This preassembly is then inserted through the opening in the i afterbody and the bellcrank inserted into thebushing .74. The bellcrank is rotated into proper angular position'relative to the flap 34, and the teeth of the face splines are brought into preliminary registration. The threads of the screw 72 are engaged with;,the threads of the flap 34 and bellcrank 70.

Because one set of threads has a pitch" different from the, 'other,.rotation of the screw 72 draws thebellcrank 'il) toward the flap 34. Thescrew 72 has internalsplines 9 2 which receive a torquing tool that would be introduced through the end of the bellcrank. The torquing tool would berotated bya torque face splines and 'the bushingflange 76. The remaining assembly steps, including later attachmentof the bevel gear segmems'sa to the bellcranks' 70, should be readily apparent.

Other features of the presentinvention arefound in the providedforvariousportions of themodulation'of 'co" ling-arr v v 4 nozzle. For long life and reliabilityf ifis' desirable. to7cool the e assembly "of en:- 94 which is appropriately connected to asourceofzcoolingrair; in wthe. usualcircumstance this source.would. be -compressor 1 '-=discharge air. In the open, normal supersonic tpositioni ofithe flaps 38, slots 96 in the rounded end of the flap rcgisterzwith slots 98 in the seat 52, therebyconnecting the-hollow interior of the flapzto the plenum chamber=94 The innerl surfaces of the flaps may be formed by separate, thin sheetrmetal plates, althoughthe drawings indicate an:integral'-.construction as a matter of*convenience. In any event, theicogling rair passes through the interior 'of'cach flap" and.- th'en-zthrpugh ap- 6 propriately located holes 100 (only a few "representative holes are shown) to form a thin film of coolant on the surfaces of the flap that require cooling; -3

' When the flaps 38 are pivoted inwardly in normal subsonic operation; theslots 96 move out of alignmentswithrthe slots 98 ndf cooling airflow'is automatically'shut off.'-By thus'-shutting off compressorbleed air, operation atsubsonic i1elocities is made more efflcient and ec'onomical'.

The frame 46 also'comprises an outer plenumichamber 102 FIGS; 11 and 12) which is appropriately connected to a so "do of c'oolingair; again compressor discharge air'would be a al'source. The plenum 102 eittends throug' h the afterbfodies 3211p to a valving arrangementincorporated into the b'ellcranks 70. This plenum is sealed at thea'ctua'tors'48 by ribs 104 which engage the spherical shell 60iThe plenum is also sealed at eachactuator (FIG; 15) by'actuatorrilis-l 05 enerical'shell 106;com os'ns yrenned drrtne frame gaging a sph 46'aiid the'afterbody castings 47.

i Cooling air is thus ducted through thep count 02; beneath the actuators so to slots 10s nemesis a saw- 40' receives the inner end "of the bellcrank l regime, slotsllo, in eachbellcrank70fregister 108. Cooling arrows flows from the plenum It) crank 70. From there the airfldw splits'with" ,through the screw 72 and flap shaftdtl tdth "flap 34 and th'eremaihing airpas'ses ing 12in the gear segrrint 84 and then raisins interior of the afterirody astin gs"4 7. The oriflce pc "112 sized to obarrr a prox mately equal cooling air he flaps 34 width: afterbody castiri'gs'47 I The inner surfaces of the afterbo dy castin "yalsp be formedas separatethihshee pa nels would be providedtwit hfsrnall hole ducted thereto, and dischargedthe'refro 7, 315,5 coolin gfilmonthe ties e pes Th a s. rrans m' miis the coding airflow.througha relatively'h a Qo'fthef flaps 34 consistent wit ivenj enginejcycle. ln'the 2 34, indicated by the inter ed to b s a in 1 the s the slots 1 03. Cooling air is" thus s ut economical operation atsubsoniccru ise Ih sva v serenad a asses l tt n t -s ath,

lustrated by the extreme dottedpgsr sis. s and ;by- Fl G.. l6. ln rm displaced to th eirextreme ..-.-..,.1 as str "latera y a d-t sflfl lotsal l aveb rot ed.v jacent slots 108. Cooling air is a e flec the hot be gs tion the rovided to ana afterbodies. This ring connects the ends of the afterbodies and overlies the ends of the flaps 34 to provide a hoop structure which can also be employed to prevent the tendency of the afterbodies 32 and flaps 34 to spread outwardly, particularly in the supersonic regime.

The described embodiments are illustrative, and variations thereof will occur to those skilled in the art within the scope of the present inventive concepts which are to be interpretted solely from the appended claims.

Having thus described the invention, what we claim as novel and desired to be secured by Letters Patent of the United States in:

I. A propulsion nozzle comprising,

a convergent portion into which a high energy gas stream is introduced,

a plurality of afterbodies projecting downstream from said convergent portion, said afterbodies being angularly spaced from each other about the axis of said convergent nozzle portion, said afterbodies having inner surfaces which are divergently tapered from a nozzle throat at the downstream end of said convergent portion,

secondary flap means disposed in the spaces between said afterbodies and extending from said throat to the downstream ends of adjacent inner surfaces of the after- ;bodies, said secondary flaps forming, in combination with isaid afterbodies, a divergent nozzle portion for expansion of said gas stream to a supersonic velocity, said secondary lflaps being displaceable to positions in which their upstream ends introduce air, at said throat, along their inner surfaces and their downstream ends move inwardly, the combination of which reduces the nozzle discharge area for propulsion with subsonic and reduced supersonic gas stream velocities.

2. A propulsion nozzle as in claim I wherein,

the outer surfaces of the afterbodies are generally parallel to the nozzle axis and extend upstream of the convergent nozzle portion and ramp means respectively between said afterbodies incline inwardly from the upstream portions of the outer surfaces of the afterbodies to facilitate the introduction of air along the inner surfaces of said secondary flap means when said flap means are so displaced.

3. A propulsion nozzle as in claim 2 wherein,

said secondary flap means are in the form of single, relatively thin airfoils disposed respectively between each adjacent pair of afterbodies, and said secondary flaps are pivoted intermediate their respective ends, relative to said afterbodies to provide for said flap means displaceability and the ramp means extend to the upstream ends of said secondary flaps when said secondary flaps are aligned with the inner surfaces of said afterbodies.

4. A propulsion nozzle as in claim 2 wherein,

the secondary flap means comprise single flaps disposed respectively between each adjacent pair of afterbodies,

said flaps have outer surfaces generally aligned with the outer surfaces of said afterbodies and the outer surfaces of the secondary flaps extend to the upstream ends of said ramp means when the inner surfaces of the secondary flaps are aligned with the inner surfaces of the afterbodies.

5. A propulsion nozzle as in claim 2 wherein,

the convergent nozzle portion comprises a plurality of primary flaps pivotable to vary the discharge area of the convergent noule portion,

said primary flaps being respectively radially aligned with said afterbodies and said secondary flap means, and

the primary flaps, aligned with said secondary flap means, forming the downstream end portions of said ramp means.

6. A propulsion nozzle as in claim 2 wherein,

the convergent nozzle portion comprises a plurality of pri mary flaps pivotal to vary the discharge area of the con vergent nozzle portion,

said primary flaps underlying and spaced inwardly from said ramp means, and means for introducing secondary air between said ramp means and said primary flaps. 7. A propulsion nozzle as in claim 2, in further combination with a pod which provides a housing for an engine generating the high energy gas stream, and wherein,

the outer surfaces of said afterbodies are formed as aerodynamic continuations of said pod.

8. A propulsion nozzle as in claim I, further comprising,

a plug forming an annular discharge nozzle area in combination with said convergent portion and said afterbodies and secondary flap means, said plug being convergently tapered in a downstream direction.

9. A propulsion nozzle as in claim 8 wherein,

said secondary flap means comprise single flaps disposed respectively between each adjacent pair of afterbodies, which secondary flaps are displaceable to positions in which their downstream ends engage said plug to divert the gas stream laterally and forwardly from the nozzle to provide reverse thrust.

10. A propulsion nozzle as in claim 9 wherein,

the flaps have tapered wings underlying said afterbodies and providing a complete blockage of the gas stream to thereby obtain maximum reverse thrust energy.

II. A propulsion nozzle as in claim l0 wherein,

the outer surfaces of the afterbodies are generally parallel to the nozzle axis and extend upstream of the convergent nozzle portion and ramp means between each afterbody are inclined inwardly from the upstream portions of the outer surfaces of the afterbodies to facilitate the introduction of air along the inner surfaces of said secondary flaps when said flaps are so displaced for propulsion with subsonic and reduced supersonic gas stream velocities and, further, to facilitate lateral discharge of the high energy gas stream when the secondary flaps are displaced to engage said plug to divert the gas stream laterally.

12. A propulsion nozzle as in c aim 1. wherein,

the secondary flap means comprise single flaps disposed respectively between each adjacent pair of afterbodies means are provided for pivotally mounting the secondary flaps, intermediate their lengths, on said afterbodies to provide for displacement thereof and actuator means are housed within said afterbodies for controlling pivotal movement of said flaps.

13. A propulsion nozzle as in claim 12 wherein,

the secondary flap actuator means comprise individual actuators respectively connected to opposite sides of each of said flaps through the pivotal mounting means.

14. A propulsion nozzle as in claim 12 wherein,

the secondary flaps have shaft means extending between the pivotal mounting means of each afterbody and the pivotal mounting means are axially locked between the flaps and the afterbodies to form a transverse, structural hoop minimizing the tendency of the afterbodies to spread outwardly when loaded by the forces of the hot gas stream.

15. A propulsion nozzle as in claim 14 wherein,

the actuator means comprise a pair of actuators mounted within each afterbody and the pivotal mounting means comprise a bellcrank having a face spline connection with each end of the shaft means of each secondary flap,

said bellcranks being journaled within said afterbodies and respectively connected to the actuators within the afterbodies, 4

said bellcranks further having flanges preloaded into engagement with structural portions of the afterbodies as part of the referenced structural hoop.

16. A propulsion nozzle as in claim 15 wherein,

a geared interconnection is provided between the bellcranks within each afterbody to assure simultaneous pivotal movement of said secondary flaps.

17. A propulsion nozzle as in claim 12 wherein,

a cooling air plenum chamber is provided in each afterbody and the pivotal mounting means include valve means for directing cooling air to the secondary flaps when the secondary flaps are positioned for expansion of the gas stream at supersonic velocity, said valve means automatically shutting off cooling airflow to the secondary flaps when the secondary flaps are pivoted for propulsion with reduced gas stream velocities.

18. A propulsion nozzle as in claim 17 further comprising,

a plug, forming an annular discharge nozzle in combination 1 with said convergent portion and said afterbodies and said secondary flaps, said plug being convergently tapered in a downstream direction,

said secondary flaps being pivotable by the same actuator means to positions in which their downstream ends engage said plug to divert the gas stream laterally and forwardly from the nozzle to provide reverse thrust, and further wherein,

the valve means automatically introduce cooling air into the secondary flaps when the secondary flaps are so pivoted for reverse thrust.

19. A propulsion nozzle as in claim 17 wherein,

the pivotal mounting means comprise a bellcrank connected to each side of each secondary flap, said bellcranks being journaled within the respective adjacent afterbodies and connected to said actuator means and said bellcranks and afterbodies have cooperative slots forming valve means for so regulating cooling airflow.

20. A propulsion nozzle as in claim 12 wherein,

the convergent nozzle portion is formed by a plurality of primary flaps with individual flaps being pivotably mounted respectively beneath each afterbody and in alignment with said secondary flaps,

sealing means interconnecting said primary flaps, and

actuator means mounted within each afterbody and connected to the respective flaps therebeneath to thereby vary the discharge area of the convergent nozzle portion.

21. A propulsion nozzle as in claim 12 further comprising,

a plug forming an annular discharge nozzle in combination with said convergent portion and said afterbodies and said secondary flaps, said plug being convergently tapered in a downstream direction,

said secondary flaps being pivotable by the same actuator means to positions in which their downstream ends engage said plug to divert the gas stream laterally and forwardly from the nozzle to provide reverse thrust.

22. A propulsion nozzle as in claim i wherein,

the upstream portions of the afterbodics are formed by a cylindrical frame structure and structural hoop means interconnect the afterbodies downstream of said cylindrical frame structure to minimize the cantilever loadings of said afterbodies on said frame structure.

23. A propulsion nozzle as in claim 22 wherein,

the structural hoop means comprise a relatively thin airfoil interconnection between the extreme downstream ends of said afterbodies.

24. A propulsion nozzle as in claim 22 wherein,

said secondary flaps are pivotally mounted on said afterbodies and said pivotal mountings comprise said hoop structure through said afterbodies. 

1. A propulsion nozzle comprising, a convergent portion into which a high energy gas stream is introduced, a plurality of afterbodies projecting downstream from said convergent portion, said afterbodies being angularly spaced from each other about the axis of said convergent nozzle portion, said afterbodies having inner Surfaces which are divergently tapered from a nozzle throat at the downstream end of said convergent portion, secondary flap means disposed in the spaces between said afterbodies and extending from said throat to the downstream ends of adjacent inner surfaces of the afterbodies, said secondary flaps forming, in combination with said afterbodies, a divergent nozzle portion for expansion of said gas stream to a supersonic velocity, said secondary flaps being displaceable to positions in which their upstream ends introduce air, at said throat, along their inner surfaces and their downstream ends move inwardly, the combination of which reduces the nozzle discharge area for propulsion with subsonic and reduced supersonic gas stream velocities.
 2. A propulsion nozzle as in claim 1 wherein, the outer surfaces of the afterbodies are generally parallel to the nozzle axis and extend upstream of the convergent nozzle portion and ramp means respectively between said afterbodies incline inwardly from the upstream portions of the outer surfaces of the afterbodies to facilitate the introduction of air along the inner surfaces of said secondary flap means when said flap means are so displaced.
 3. A propulsion nozzle as in claim 2 wherein, said secondary flap means are in the form of single, relatively thin airfoils disposed respectively between each adjacent pair of afterbodies, and said secondary flaps are pivoted intermediate their respective ends, relative to said afterbodies to provide for said flap means displaceability and the ramp means extend to the upstream ends of said secondary flaps when said secondary flaps are aligned with the inner surfaces of said afterbodies.
 4. A propulsion nozzle as in claim 2 wherein, the secondary flap means comprise single flaps disposed respectively between each adjacent pair of afterbodies, said flaps have outer surfaces generally aligned with the outer surfaces of said afterbodies and the outer surfaces of the secondary flaps extend to the upstream ends of said ramp means when the inner surfaces of the secondary flaps are aligned with the inner surfaces of the afterbodies.
 5. A propulsion nozzle as in claim 2 wherein, the convergent nozzle portion comprises a plurality of primary flaps pivotable to vary the discharge area of the convergent nozzle portion, said primary flaps being respectively radially aligned with said afterbodies and said secondary flap means, and the primary flaps, aligned with said secondary flap means, forming the downstream end portions of said ramp means.
 6. A propulsion nozzle as in claim 2 wherein, the convergent nozzle portion comprises a plurality of primary flaps pivotal to vary the discharge area of the convergent nozzle portion, said primary flaps underlying and spaced inwardly from said ramp means, and means for introducing secondary air between said ramp means and said primary flaps.
 7. A propulsion nozzle as in claim 2, in further combination with a pod which provides a housing for an engine generating the high energy gas stream, and wherein, the outer surfaces of said afterbodies are formed as aerodynamic continuations of said pod.
 8. A propulsion nozzle as in claim 1, further comprising, a plug forming an annular discharge nozzle area in combination with said convergent portion and said afterbodies and secondary flap means, said plug being convergently tapered in a downstream direction.
 9. A propulsion nozzle as in claim 8 wherein, said secondary flap means comprise single flaps disposed respectively between each adjacent pair of afterbodies, which secondary flaps are displaceable to positions in which their downstream ends engage said plug to divert the gas stream laterally and forwardly from the nozzle to provide reverse thrust.
 10. A propulsion nozzle as in claim 9 wherein, the flaps have tapered wings underlying said afterbodies and providing a complete blockage of the gas stream to thereby obtain maximum Reverse thrust energy.
 11. A propulsion nozzle as in claim 10 wherein, the outer surfaces of the afterbodies are generally parallel to the nozzle axis and extend upstream of the convergent nozzle portion and ramp means between each afterbody are inclined inwardly from the upstream portions of the outer surfaces of the afterbodies to facilitate the introduction of air along the inner surfaces of said secondary flaps when said flaps are so displaced for propulsion with subsonic and reduced supersonic gas stream velocities and, further, to facilitate lateral discharge of the high energy gas stream when the secondary flaps are displaced to engage said plug to divert the gas stream laterally.
 12. A propulsion nozzle as in claim 1 wherein, the secondary flap means comprise single flaps disposed respectively between each adjacent pair of afterbodies means are provided for pivotally mounting the secondary flaps, intermediate their lengths, on said afterbodies to provide for displacement thereof and actuator means are housed within said afterbodies for controlling pivotal movement of said flaps.
 13. A propulsion nozzle as in claim 12 wherein, the secondary flap actuator means comprise individual actuators respectively connected to opposite sides of each of said flaps through the pivotal mounting means.
 14. A propulsion nozzle as in claim 12 wherein, the secondary flaps have shaft means extending between the pivotal mounting means of each afterbody and the pivotal mounting means are axially locked between the flaps and the afterbodies to form a transverse, structural hoop minimizing the tendency of the afterbodies to spread outwardly when loaded by the forces of the hot gas stream.
 15. A propulsion nozzle as in claim 14 wherein, the actuator means comprise a pair of actuators mounted within each afterbody and the pivotal mounting means comprise a bellcrank having a face spline connection with each end of the shaft means of each secondary flap, said bellcranks being journaled within said afterbodies and respectively connected to the actuators within the afterbodies, said bellcranks further having flanges preloaded into engagement with structural portions of the afterbodies as part of the referenced structural hoop.
 16. A propulsion nozzle as in claim 15 wherein, a geared interconnection is provided between the bellcranks within each afterbody to assure simultaneous pivotal movement of said secondary flaps.
 17. A propulsion nozzle as in claim 12 wherein, a cooling air plenum chamber is provided in each afterbody and the pivotal mounting means include valve means for directing cooling air to the secondary flaps when the secondary flaps are positioned for expansion of the gas stream at supersonic velocity, said valve means automatically shutting off cooling airflow to the secondary flaps when the secondary flaps are pivoted for propulsion with reduced gas stream velocities.
 18. A propulsion nozzle as in claim 17 further comprising, a plug, forming an annular discharge nozzle in combination with said convergent portion and said afterbodies and said secondary flaps, said plug being convergently tapered in a downstream direction, said secondary flaps being pivotable by the same actuator means to positions in which their downstream ends engage said plug to divert the gas stream laterally and forwardly from the nozzle to provide reverse thrust, and further wherein, the valve means automatically introduce cooling air into the secondary flaps when the secondary flaps are so pivoted for reverse thrust.
 19. A propulsion nozzle as in claim 17 wherein, the pivotal mounting means comprise a bellcrank connected to each side of each secondary flap, said bellcranks being journaled within the respective adjacent afterbodies and connected to said actuator means and said bellcranks and afterbodies have cooperative slots forming valve means for so regulating cooling airflow.
 20. A propulsion nozzle as in claim 12 wherein, the convergent nozzle portion is formed by a plurality of primary flaps with individual flaps being pivotably mounted respectively beneath each afterbody and in alignment with said secondary flaps, sealing means interconnecting said primary flaps, and actuator means mounted within each afterbody and connected to the respective flaps therebeneath to thereby vary the discharge area of the convergent nozzle portion.
 21. A propulsion nozzle as in claim 12 further comprising, a plug forming an annular discharge nozzle in combination with said convergent portion and said afterbodies and said secondary flaps, said plug being convergently tapered in a downstream direction, said secondary flaps being pivotable by the same actuator means to positions in which their downstream ends engage said plug to divert the gas stream laterally and forwardly from the nozzle to provide reverse thrust.
 22. A propulsion nozzle as in claim 1 wherein, the upstream portions of the afterbodies are formed by a cylindrical frame structure and structural hoop means interconnect the afterbodies downstream of said cylindrical frame structure to minimize the cantilever loadings of said afterbodies on said frame structure.
 23. A propulsion nozzle as in claim 22 wherein, the structural hoop means comprise a relatively thin airfoil interconnection between the extreme downstream ends of said afterbodies.
 24. A propulsion nozzle as in claim 22 wherein, said secondary flaps are pivotally mounted on said afterbodies and said pivotal mountings comprise said hoop structure through said afterbodies. 